Gaming devices such as slot machines and other video forms of gaming devices (e.g., video poker, video keno, video slots, etc.) are known. In general, a gaming device allows a player to play a game in exchange for a wager (a monetary amount placed at risk). Depending on the outcome of the game, the player may be entitled to an award which is paid to the player by the gaming device, normally in the form of currency or game credits.
For example, a conventional slot machine contains a plurality of wheels, each wheel bearing a set of symbols. The configuration of symbols on each wheel determines a probability of obtaining any particular combination of symbols when playing the machine. Each combination is mapped, or associated with, an award. The machine includes, implicitly or explicitly, a “pay table” which shows the award associated with each combination. When a player achieves a given combination, the machine maps that combination to the appropriate award (which may be zero), and pays the player accordingly. The wheel or reels of a slot machine may be convention physical reels or may be a video representation of reels displayed on a display device or monitor.
Pay tab les associated with the game define the award amounts corresponding to matching symbols on pay lines. An illustrative pay table for a three-reef arrangement is shown in Table 1.
TABLE 1SymbolAward77725BBB10CCC5MMM3Mixed0
The pay table of Table 1 shows the award associated with each symbol. The term “mixed” refers to all combinations not explicitly shown. It is assumed that on each play, the player wagers at least one unit, and the award is measured in terms of the same units. Of course, a game may be structured such that more than one wilt can be wagered at one time, in which case the awards can be multiplied by the number of units wagered.
In the above example, there are five possible awards, namely 25, 10, 5, 3, and 0. The likelihood a particular award event will occur during the course of play is normally defined by a probability distribution. For example, the probability of obtaining each possible award could be determined according to the distribution shown in Table 2:
TABLE 2AwardProbability25.0110.035.053.060.85
In the example probability distribution of Table 2, the likelihood of obtaining a symbol combination of 777 (having an associated award of 25), also sometimes referred to as “hit frequency”, is 1 in 100 games. Likewise, the likelihood of obtaining a symbol combination of BBB (having an award of 10) is a hit frequency of 3 in 100 games; the likelihood of obtaining a symbol combination of CCC (having an award of 5) is a hit frequency of 5 in 100 games; the likelihood of obtaining a symbol combination of MMM (having an award of 3) is a hit frequency of 6 in 100 games; the likelihood of obtaining a mixed-symbol combination (having an award of zero (0)) is 85 in 100 games. According to this example, the mean award would be 0.98, with a standard deviation of about 3.17. Thus, when a player wagers one unit, the expected payback is 0.98 units. Through appropriate random number generators, the gaming device derives a combination of symbols which is displayed to the user, and this symbol combination is mapped to an award which is then paid to the player.
By so constructing the award pay out for each winning outcome and its hit frequency (probability of occurrence), the overall performance for the gaming device can be defined. By summing the product of hit frequency and award for outcomes, the device's performance can be defined. Thus the device's performance (Px) may be represented by the following expression,Σ(hit frequency×award) 
For example, when it is said that a gaming device has a performance of a 98% pay back machine, than means that multiplying the hit frequency for each outcome times the award and summing those products, the performance Px can be defined such that for every unit wagered, the device statistically should pay back 0.98 units.
In order to increase revenue for the operation of gaming devices, various means for increasing player interest and participation in gaming devices have been attempted. For example, U.S. Pat. No. 5,397,125 to Adams discloses a gaming device which dispenses awards in the multiple forms: one form is currency and another form of payout comprises tokens formed of a precious metal such as silver and/or gold. Each token award would have a corresponding entry in the pay table equivalent to the value of the token award. Under this arrangement, the pay table would be modified to include pay outs for the token awards. Thus an illustrative modified pay table would look like Table 3.
TABLE 3SymbolAward777Gold TokenBBBSilver TokenCCC5MMM3Mixed0
In Table 3, the Gold Token award substitutes for the 25 unit award (of Table 1), and the Silver Token award substitutes for the 10 unit award (of Table 1). A corresponding modified probability table is illustrated in Table 4.
TABLE 4AwardProbabilityGold Token.01Silver Token.035.053.060.85
Since the Gold Token award has an equivalent value of 25 units, and the Silver Token award has an equivalent value of 10 units, the overall payback probability in terms of “unit value” is the same as that of Table 2, namely 0.98 (i.e. a 98% pay back machine).